Progress in indirect and direct-drive planar experiments on hydrodynamic instabilities at the ablation front

Abstract

Understanding and mitigating hydrodynamic instabilities and the fuel mix are the key elements for achieving ignition in Inertial Confinement Fusion. Cryogenic indirect-drive implosions on the National Ignition Facility have evidenced that the ablative Rayleigh-Taylor Instability (RTI) is a driver of the hot spot mix. This motivates the switch to a more flexible higher adiabat implosion design [O. A. Hurricane et al., Phys. Plasmas 21, 056313 (2014)]. The shell instability is also the main candidate for performance degradation in low-adiabat direct drive cryogenic implosions [Goncharov et al., Phys. Plasmas 21, 056315 (2014)]. This paper reviews recent results acquired in planar experiments performed on the OMEGA laser facility and devoted to the modeling and mitigation of hydrodynamic instabilities at the ablation front. In application to the indirect-drive scheme, we describe results obtained with a specific ablator composition such as the laminated ablator or a graded-dopant emulator. In application to the direct drive scheme, we discuss experiments devoted to the study of laser imprinted perturbations with special phase plates. The simulations of the Richtmyer-Meshkov phase reversal during the shock transit phase are challenging, and of crucial interest because this phase sets the seed of the RTI growth. Recent works were dedicated to increasing the accuracy of measurements of the phase inversion. We conclude by presenting a novel imprint mitigation mechanism based on the use of underdense foams. The foams induce laser smoothing by parametric instabilities thus reducing the laser imprint on the CH foil. V C 2014 AIP Publishing LLC. [http://dx.

Direct Laser Writing of Low‐Density Interdigitated Foams for Plasma Drive Shaping

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From ICF to laboratory astrophysics: ablative and classical Rayleigh–Taylor instability experiments in turbulent-like regimes

“…The laser pulse is shaped in time to create a radiative temperature plateau lasting 12 ns. This is 4-times longer compared to previous similar ID configurations on OMEGA [28]. The accelerated package is glued on the radiation exit hole opposite to laser entrance hole.…”

Recent progress in quantifying hydrodynamics instabilities and turbulence in inertial confinement fusion and high-energy-density experiments

“…Perturbations induced by 3D capsule surface roughness [67], as well as inner DT ice modulations, were quantified [68]. Hydrodynamics instabilities can be increased by feed-through processes at various interfaces [69]. The fill tube is also a localized defect and even its X-ray shadow is detrimental [70,71].…”